There are several spatially segregated and functionally distinct subpopulations of taste buds in the mouth. Most studies of central gustatory physiology have investigated responses arising from just one of them, the taste buds on the anterior tongue, which account for less than 15 % of all taste buds. Much less is known about the chemosensitive response profiles of central neurons that receive afferent information from other taste receptor subpopulations, interactions between them, or about the organization of central pathways as it relates to these distinct taste bud groups. The long-term goal of the work described in this proposal is to provide a comprehensive description of the central processing of gustatory information, which encompasses all oral taste buds. These experiments will use both neurophysiological and neuroanatomical techniques to accomplish this goal in the first- and second-order gustatory relay nuclei in the brainstem, the nucleus of the solitary tract (NST) and the parabrachial nuclei (PBN). First, these experiments will define the chemosensitive response profiles of NST neurons that respond to a neglected set of taste bud subpopulations, those in the posterior oral cavity. Second, they will elucidate principles of how NST neurons integrate spatially-convergent gustatory information. Third, they will describe how receptive field organization and representation change at the next synaptic relay, the PBN. Finally, these experiments will explore relationships between the afferent and efferent characteristics of brainstem gustatory neurons, to provide a more complete context for understanding their function. The gustatory system plays an important role in modulating eating behavior; in particular it is important in determining what and how much is eaten. Food choice has an impact on several health problems, including obesity, hypertension and cancer. Understanding the initial processing of gustatory signals provides a necessary basis for understanding the higher-level processing that influences complex behavioral acts.